Abstract
IN the past two decades, the infant mortality rate (deaths under one year of age per thousand live births) in the United States has declined sharply. Now well established, this trend has elicited great interest, in part because it follows a period of almost equal duration when the infant mortality rate remained relatively constant despite intense efforts to lower it. The current decline in infant mortality has led to questions about the efficacy of preventive services in the antenatal period, the role of perinatal intensive-care services, and the implications of changes in infant mortality for the burden of morbidity in . . .